The present invention pertains to a positioning control system for maintaining the feed bar of a rock drill apparatus in a predetermined directional attitude when the feed bar suppporting member is moved from one position to another.
In the art of rock drilling it is often desirable to drill a series of blast holes in a particular pattern in order to facilitate efficient rock breakage and removal and to maintain the shape of a tunnel bore or quarry wall. Drill hole patterns wherein a number of holes are drilled parallel to each other are common. Accordingly, it is desirable to be able to rapidly and accurately position the drill feed bar to assure that each hole, as it is drilled, is parallel to the other holes.
To this end a number of inventions have been developed for use with movable drill boom and feed bar apparatus with the intended purpose of positioning the feed bar in response to movement of the boom to maintain the drilling axis parallel to previously drilled holes as well as at a predetermined directional attitude with respect to the rock face.
U.S. Pat. No. 3,374,975 to H. Bronder discloses an arrangement of parallelogram linkages associated with the boom. The above mentioned patent also discloses an arrangement of flow connected actuators associated with the boom and the positioner device for the feed bar. The disadvantages of the above mentioned devices include those of excess weight and limited range of movement, particularly for the mechanical linkage arrangement. Moreover, the flow connected actuators are susceptible to positioning errors due to fluid leakage and geometric considerations.
U.S. Pat. No. 3,481,409 to B. A. Westerlund discloses a parallel positioning system including electrical sensors mounted on the boom pivots and the pivots of the feed bar positioner mechanism. Such electrical devices are generally unsuited for the harsh operating environment of rock drilling equipment. Moreover, it is advantageous to provide control systems which are as simple and easily maintained as possible and which are similar in character with the type of equipment with which such control systems are used. These desirable features of a parallel positioning control system are provided for with the invention disclosed and claimed herein.